ML20085E428

LER ER-76-045:on 761209,DBA Sequencer 34-1 Failed to Operate During Quarterly Safeguards Test Rerun.Caused by Failure of Sequencer Clutch to Reset Due to Insufficient Clutch Disk Gap to Set Screw Slippage

ML20085E428
Person / Time
Site:	Palisades
Issue date:	12/21/1976
From:	Bixell D CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.)
To:	James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML20085E430	List: ML20085E428 ML20085E432
References
LER-ER-76-045, LER-ER-76-45, NUDOCS 8308110439
Download: ML20085E428 (4)

Text

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"'y T E E R!E cocx(T NUMSER EVENT DATE REPORT DATE O s COwT I . I .I [y_l LL,_J 101 s 101-10121 sl _51 1 11 a l 0191716 I I l l a l a l 11716 7 8 57 58 59 80 81 88 89 74 75 8C EVENT DESCRIPTION BE l During a rerun of a test (to check other equipment) which was successfully conducted t 7 89 8C 3[ l about one day earlier. DBA sequencer 3h-1 failed to operate. In accordance with the 7 89 8; 3[ l Technical Specifications the redundant channel was then tested and similarly DBA se-7 89 8 3G lquencer 34-2 failed to onerate. With this second fcilure a standard (normal) plant 7 8 8,

@9 7 89 l shutdown was commenced. See attached Event Description for more details.

pnug (ER-76-h5) 8L NE coc'E COMPONENT c00E VOLATUN BE l E l E l {

7 89 10 11 l Il N I S l Tl Rl UI 12 17 lAl 43 44 lEl0l2l0l 47 W48 CAUSE DESCAPTION UG l The sequencer clutch failed to reset due to insufficient clutch disk gap. The most  !

7 89 BC h l probable cause of the disk gan problem was set screw slippage. See Event Description l 7 89 8C M ifor additional details. l

1. N s s power OTNER status Esc 0vERv' cecovERv otscRiPTcN H

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REL 5 0 AMOUNT OF aCTMTY LOCATON OF RELEASE 3E l2 f0 L3] EASE l NA l l NA l 7 8 9 10 11 44 45 8C PERSONNEL EXPOSURES NUMt5A TYPE DESCR97CN M l 01010 I l.lj l NA l 7 89 11 12 13 80 PERSONNEL INJURIES NUMSER DESCRIPTON 3C l 0l 0l 0l l NA l 7 89 11 12 -

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' Probable Consequences ,

DE I If an SIS would have occurred and standby power were not available (Conta on Line 18) l 7 89 80 LOSS OR OAMAGE TO FACILITY TYPE DESCRIPTON 8 Lz.J l n^ l 7 89 10 80 PU8UCITY H INcne l 7 89 80 ADDITIONAL FACTORS g[ l(Contd From Line 15) some safety-related equipment would have had to be manually started.l

7 89 80 G308110439 761221 PDR ADOCK 05000255 31 7 89 S PDR __

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. s O O LICENSEE EVENT REPORT ER-76-45 Docket 50-255 Continuation of Event Description

Background

On December 8, 1976, the quarterly safeguards test (QO-1) was conducted success-fully except for one discrepancy (charging pump P55C should not have started).

Part of the evaluation of this deviation required a rerun of a portion of the test to verify the cause of the pump start. At 1118 hours0.0129 days <br />0.311 hours <br />0.00185 weeks <br />4.25399e-4 months <br /> on December 9, the test was run and it was found that one of the two left channel DBA sequencers (3h-1) failed to operate. Repair personnel were promptly notified of the problem and cor-rective action was initiated.

Initial Action In accordance with Technical Specifications, the operability of the right channel SIS /DBA sequencer was determined prior to commencing the repair of the left chan-nel. At 1222 hours0.0141 days <br />0.339 hours <br />0.00202 weeks <br />4.64971e-4 months <br />, the right channel portion of QO-1 was run and it was found that one of the two right channel sequencers (3k-2) alsc failed to operate. Based on this additional failure, reactor shutdown was commenced and the normal shutdown rate was established by 1250 hours0.0145 days <br />0.347 hours <br />0.00207 weeks <br />4.75625e-4 months <br />. Concurrent with the shutdown, repair of the right channel sequencer was begun.

Findings Upon inspection of the sequencer, it was determined that the clutch was still engaged and that the unit had failed to reset. The unit was reset and the clutch gap adjusted. At approximately 1315 hours0.0152 days <br />0.365 hours <br />0.00217 weeks <br />5.003575e-4 months <br /> the right channel portion of QO-1 was run to verify proper operation of 3h-2. The test was successful and proper reset of the unit was observed. The test was rerun a second time and again successful operation of the unit was observed.

Upon completion of repair and testing of che right channel, the failed left chan-nel sequencer (34-1) was investigated. The unit was found to have the same prob-lems as 34-2 and it was repaired and tested. By approximately 1400 hours0.0162 days <br />0.389 hours <br />0.00231 weeks <br />5.327e-4 months <br />, both channels had been repaired, tested, and returned to service.

Evaluation and Follow-Up The clutch disk assemblies for sequencers 34-2 and 3h-1 had been previously re-placed and adjusted on October 5,1976 and October lk,1976, respectively. At this time, the clutch disk clearance was set at approximately 0.020". The unit was tested several times and QO-1 was used for the operational check of the com-pleted work. Satisfactory operation was obtained in each case. (It should be noted that the clutch disk gap setting is the result of a trade off between (1) a large gap which insures easy resetting of the unit and (2) a small gap which results in greater spring tension producing a minimum of clutch slippage.)

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Since the operability of the unit was demonstrated several times after the clutch replacement, it is concluded that the clearances set during the clutch replacement were adequate. The clutch gap apparently changed during the two months following the repair preventing clutch disengagement.

Subsequent to resetting the clutch disk gap after this event, the set screws for the clutch collars were further tightened to minimize the possibility of recurrence.

In addition to the mechanical adjustment discussed above, temporary procedural controls will be instituted. For test situations requiring operation of the sequences, the sequencers will be visually inspected after sequencer operation to insure that the reset function of each unit performs satisfactorily.

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Generel Omeeen see West useNgen Averwe,Jeekeer% MooNgen 40900 e Area Ceee 917 788-0800 i

December 21, 1976 o

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Mr James G Keppler .

Office of Inspection & Enforcement Region III US Nuclear Regulatory Commission 799 Roosevelt Road Glen Ellyn, IL 60137 DOCKET 50-255, LICENSE DPR PALISADES PLANT, ER-76 DBA SEQUENCER .

Attached is a Licensee Event Report relating to the Palisades Plant. This

• report concerns failure of part of the automatic sequencer designed to place safety system loads on the emergency diesel generator. These safety systems could have been manually started should that have been required.

bat $$ 0' MJ David A Bixel Assistant Nuclear Licensin'd Administrator x

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l DEC 231976 s

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